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Six satellites, five years

COSMIC hits a milestone, looks ahead

March 15, 2011 | The GPS-based satellite observing system known as COSMIC will celebrate its fifth anniversary on April 15. About ten staff from UCAR’s COSMIC Program Office will be in Taipei, Taiwan, April 13–15 for the annual data users’ workshop, which is sponsored by Taiwan’s National Space Organization. A special reception is being planned by NSPO to celebrate COSMIC’s birthday.

“This is a major milestone. COSMIC has accomplished all the science objectives it set out to do, and has convincingly demonstrated the power of GPS radio occultation for research and operations,” says Bill Kuo, who has led COSMIC at UCAR since 1998.

The satellites’ five-year anniversary corresponds with the end of the mission’s design life. In April 2006, COSMIC (the Constellation Observing System for Meteorology, Ionosphere & Climate), a joint U.S./Taiwan project, launched six satellites into orbit around Earth. The mission employs a method called GPS radio occultation to measure how much a GPS signal is bent when its satellite is occulted by Earth’s atmosphere. The researchers then apply scientific data processing algorithms to the data to determine underlying atmospheric conditions, such as profiles of air density, temperature, moisture, and electron density in the ionosphere.

By tracking up to 2,500 atmospheric soundings every 24 hours in a nearly uniform distribution around the globe, COSMIC’s coverage easily surpasses traditional weather balloons and monitoring stations. It was launched as a research, not operational, system, and yet the technology has been so successful that the data are being used around the world for operational forecasting, with numerical weather prediction centers assimilating the data into their models and reporting positive impacts on forecasts.

“It’s unprecedented that a new observational system comes online and major global weather centers start assimilating its data within a year after launch,” says COSMIC’s Bill Schreiner.

These maps show the number and geographic distribution of predicted soundings that occur in a three hour period for COSMIC and COSMIC-2. The COSMIC satellites have produced up to 2,500 soundings in 24 hours; COSMIC-2 could produce more than 8,000 per day. (Images courtesy Bill Schreiner/COSMIC.)

The next step: COSMIC-2

A follow-on operational mission, known as COSMIC-2, was included in NOAA’s fiscal year 2011 budget that is awaiting approval by Congress. The current mission plan is to launch two sets of six satellites. The first set, scheduled for a 2015 launch, will go into equatorial orbits to provide high-density measurements in the tropics. The second set, scheduled for 2017, will go into polar orbits. The satellites will fly a new receiver developed at NASA’s Jet Propulsion Laboratory called Tri-G (Tri Global Navigation Satellite System) that will track not only GPS signals but also Russia’s GLONASS navigation system and Europe’s upcoming Galileo system.

“With Tri-G tracking signals from at least two transmitting systems, COSMIC-2 could retrieve more than 8,000 soundings per day, whereas COSMIC tracking GPS has only currently provided up to 2,500 per day,” Bill says. “That’s a lot more data and it will have more impact on the science.”

COSMIC-2 is a partnership between NOAA and NSPO, which funded much of the current COSMIC system. UCAR’s COSMIC Program Office is expected to support NOAA by serving as the COSMIC-2 data processing center.